Structural Studies of Prion Fibrils and Other Protein Fibrils

National Institute Of Diabetes And Digestive And Kidney Diseases

Investigators

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Abstract

Progress in FY2021 was in the following areas: (1) MOLECULAR STRUCTURE OF SUP35NM FIBRILS: Sup35p is the yeast protein whose intra-cellular aggregation into amyloid-like fibrils produces the transmissible PSI+ prion phenotype. Together with Reed Wickner of NIDDK, we have shown previously that Sup35NM fibrils (containing the N-terminal and middle domains of Sup35p) contain in-register parallel beta-sheets. Other aspects of Sup35NM fibril structure are unclear and controversial. We are now working towards determining the full molecular structure of Sup35NM fibrils, using cryo-EM methods. We have obtained cryo-EM images and performed preliminary analyses, which suggest a multilayered cross-beta structure with a single protofilament (consistent with our earlier mass-per-length and solid state NMR measurements). We expect this work to be completed within the next several months. (2) SOFTWARE FOR AUTOMATED PICKING OF SEGMENTS IN CRYO-EM STUDIES OF FIBRILS: The most time-consuming part of structure determinations by cryo-EM is the selection of fibril segments from thousands of images, which is usually done manually. We have developed and published a new algorithm, called FibrilFinder, that can identify well-resolved fibril segments automatically, without manual intervention or training. With minimal computational resources, FibrilFinder can analyze about 1000 images in about ten minutes, dramatically accelerating the process of image analysis.